1. Field of the Invention
The present invention relates to tracheostomy valves to be attached to a tube placed in the stoma of a patient.
2. Prior Art
A permanent tracheostoma is sometimes necessary in order to obtain adequate ventilation and to reduce dead space in patients with stenoses of the larynx or the subglottic space. It is also often indicated in cases of respiratory insufficiency due to chronic bronchitis or severe bronchial asthma, and in patients with bilateral vocal cord pareses where a laterofixation cannot be done. This has usually been achieved by the insertion of a conventional tracheostomy tube which, however, carries many problems; the ability to cough is greatly reduced when a sufficient intra-abdominal pressure cannot be acquired, speech is impaired, the tracheostomy tube has to be secured by bands around the neck and it must be changed at regular intervals, etc. The by-passing of the nose creates problems concerning the humidification of the airways.
The drawbacks of the conventional tracheostomy tube technique have encouraged the construction of a permanent tracheal cannula and to-day there are cannulas for permanent use. The cannulas are usually kept in position by an outer flange and four flaps on the tracheal side.
In order to obtain the full benefit of such permanent cannulas there is a need for disposable tracheostomy valves that facilitate speech and coughing and, additionally, prevent dehydration of the airways of the patient.